Brief Description of the Prior Art
The need for a pump capable of pumping supernatant, relatively low density, contaminant liquids from a subterranean environment in which such liquids overlie and float upon the water in a water saturated formation has recently substantially intensified. The greater emphasis on the separation from, and removal of, such liquids from ground waters has resulted in part from an enhanced sensitivity of society to the problem of maintaining fresh water supplies in an uncontaminated condition.
One category of environmental comtaminant being encountered with increasing frequency includes liquids which are insoluble in, and substantially immiscible with, water, whether fresh or saline, and which, in having a density which is different from that of water, either float on the surface of the water, or are located beneath the water by reason of being more dense than water. It is now known, for example, that adjacent to some oil and gas refineries which have operated over a period of many years, the accumulation of hydrocarbons which have leaked from tanks and pipelines in the refinery has, in some instances, constituted a serious source of contamination of aquifers and other subterranean waters. Further, the quantities of such hydrocarbons which stratify on the surface of subterranean waters have sometimes been sufficient to make their recovery an economically attractive proposition.
For the purpose of recovering hydrocarbons, or other lighter-than-water liquids from a subterranean environment where these liquids float on the ground water present, several types of specializied pumps which are well adapted to recover these liquids by pumping, following their separation from the water, have been developed.
In general, the hydrocarbons or other low density liquids are separated from water upon which such liquids float by a density difference and gravity flow technique in which the pump to be utilized is first lowered to a position in which an intake of the pump is located at approximately the location of the interface between the water and the supernatant hydrocarbon. Openings to the pump housing are provided at a level above this interface so that only hydrocarbons will flow through the openings and into the pump for purposes of removal by the pump. After a pumping chamber within the pump has been filled with the liquid which enters in the described fashion, one type of pump in use is pneumatically actuated to express or drive the liquid thus accumulated in the pump upwardly to the surface where it can be recovered at a suitable remote location. The air or other gas used to operate the pump is cyclically charged under pressure, and, alternately, is exhausted to the atmosphere during a different phase of the pump operation.
Patents which disclose pumps of the type described which are pneumatically operated to remove separated hydrocarbons by alternately charging air under pressure to the pump, and then venting air in the pump chamber to the atmosphere as the chamber is filled with hydrocarbon liquid, include U.S. Pat. No. 4,678,040 to McLaughlin et al, U.S. Pat. No. 4,546,830 to McLaughlin et al, U.S. Pat. No. 4,527,633 to McLaughlin et al, U.S. Pat. No. 129,353 to Lytle, U.S. Pat. No. 751,323 to Moran et al, U.S. Pat. No. 801,991 to Gosse, U.S. Pat. No. 2,171,402 to Muir, U.S. Pat. No. 3,894,583 to Morgan, U.S. Pat. No. 3,991,825 to Morgan and U.S. Pat. No. 4,025,237 to French.
The commercially available Pulse Pump of QED Environmental Systems, Inc., is a pneumatically controlled pump useful for the described purpose.
A pump utilizing a Teflon (polytetrafluoroethylene) bladder to intake, and then discharge, a water sample is marketed by the MIP Division of The Durison Company, Inc. of Dayton, Ohio. In this pump, the liquid to be pumped flows through a check valve into a space between the exterior of the bladder and a rigid pump housing. This causes the bladder to collapse. Air is then forced into the bladder under pressure to expel the accumulated liquid from the space between the bladder and the rigid housing.